JP6543111B2 - Screw tightening device - Google Patents

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a screw tightening device that determines whether or not the head of a screw is lifted from the upper surface of a work after tightening the screw to a work with a predetermined fastening torque.

  A conventional screwing device is disclosed in U.S. Pat. First, a conventional screw tightening device comprises a screw support means for conveying a screw, which is an example of a fastening part, to a predetermined position, a screw tightening tool for taking out a screw from the screw support means and tightening it on a work, and supporting the screw tightening tool A moving means movable to the work and the screw support means, and a control device for driving and controlling the moving means and the screw tightening tool. The screw support means is configured to be able to align and transport the head of the screw in a hanging forward direction, and comprises a receiving block for supporting the screw transported forward in a suspended state. The screw tightening tool includes a bit that fits in a fitting hole attached to the head of the screw, a bit rotation motor that rotationally drives the bit with a predetermined fastening torque and rotational speed, and the bit. A suction pipe slidable to the bit rotation motor side, a relative position detection unit capable of detecting the relative position between the bit and the suction pipe, and an air suction connected to the suction pipe and capable of suctioning air from the tip of the suction pipe And means. The control device stores the relative position between the suction pipe and the bit when the screw is taken out of the receiving block of the screw support means as the first bit position with respect to the upper surface of the receiving block and immediately after the screw is tightened to the work The relative positions of the suction pipe and the bit can be stored as second bit positions with respect to the upper surface of the work. Further, the control device obtains a difference between the first bit position and the second bit position after tightening the screw to the work, and determines whether the difference is within a preset allowable range or not. It is configured to determine the presence or absence of floating.

JP, 2013-59816, A

  As described above, the conventional screw tightening device calculates a difference between the first bit position and the second bit position after tightening a screw on a work, and further compares the difference with a preset upper / lower limit range It is determined that the screw is floating. Therefore, the conventional screw tightening device must sequentially process two steps of calculation of the difference and comparison of whether it is within the upper and lower limit range before the screw floating determination is performed after tightening to the work, There is a problem that it takes time to immediately determine the screw floating immediately after tightening.

  In addition, in the conventional screw tightening device, when taking out the screw from the screw support means, it is not judged whether this screw has the normal screw head height, so a nonstandard screw is tightened to the work and it is defective There was also a problem that flowed out to the post process. In addition, there is also a problem that the cost of the screw tightening device increases because a separate device for sorting whether or not the screw is a nonstandard screw is separately required before supplying the screw to the screw support means.

  The present invention has been made in view of the above problems, and a screw tightening tool rotatably provided with a bit engaged with a screw, and a lifting unit connected to the screw tightening tool and capable of moving up and down in the extending direction of the bit And a robot body which connects the lift unit and can move the screw tightening tool to the screw support means or the work space, and a control device for driving and controlling the robot body, the screw tightening tool, and the lift unit, A screw tightening device for taking out from the screw support means and tightening to the work, the bit relative position measuring unit measuring the elevation position of the bit as the relative position to the mounting surface of the screw support means or the upper surface of the work; The bit relative position measuring unit sets the relative position with respect to the mounting surface to a first taught relative position during teaching operation. While measuring as the first actually measured relative position at the time of actual work, while measuring the relative position to the upper surface of the work as the second taught relative position at the time of teaching work, as the second actually measured relative position at the time of the actual work A control unit configured to measure, calculate the difference between the first taught relative position and the first measured relative position, and calculate the sum of the difference and the second taught relative position; A storage unit for storing the sum as the screw lift determination reference position, and a determination unit for comparing the screw lift determination reference position with the second actual measurement relative position to determine the presence or absence of screw lift on the upper surface of the work It is characterized by

  The elevating unit comprises an elevating motor for outputting a pulse of the rotationally driven rotation to the outside, a ball screw shaft connected to the elevating motor and having a predetermined lead, and a ball screw engaged with the ball screw shaft. A movable member movable along a direction in which the screw shaft extends, and the screwing tool is attached to the movable member, and the control device changes the current supplied to the elevating motor to raise or lower the bit The thrust control unit includes: a thrust control unit that switches and controls a thrust; and a bit absolute position measurement unit that measures an absolute position of the bit relative to a waiting position of the bit based on a pulse output of the lift motor and the lead of the ball screw shaft The unit may measure the first taught relative position, the first measured relative position, the second taught relative position, and the second measured relative position before measuring the second measured relative position. It is desirable to switch control the thrust of bets from a high thrust to low thrust.

  Further, the storage unit stores a screw type determination range set in advance based on a standard dimension that defines the head height of the screw and the depth of the fitting hole of the screw to be engaged with the bit; It is preferable that the determination unit compares the screw type determination range with the first actual measurement relative position to determine the dimensions of the screw taken out from the screw support unit.

Further, the screw tightening tool slides in the extending direction of the bit and moves relative to the bit , and comprises a suction pipe capable of suctioning the screw, and the bit relative position measuring unit measures the bit You may comprise with the displacement sensor which measures the movement distance of the adsorption pipe which moved relatively with respect to it.

The elevating unit further includes an elevating motor for pulsating the amount of rotationally driven rotation to the outside, a ball screw shaft connected to the elevating motor and having a predetermined lead, and a ball screw engaged with the ball screw shaft. It comprises a movable member movable along a direction in which the screw shaft extends, and the screwing tool is attached to the movable member, and the control device controls the pulse output of the lift motor and the lead of the ball screw shaft. Based on the absolute position of the bit relative to the waiting position of the bit, and the screw tightening tool slides in a direction in which the bit extends and moves relative to the bit to move the screw Bei a detector that emits and adsorbable adsorption pipe, a detection signal to the control unit detects the suction pipe begins to move relative to the bit The bit absolute position measuring unit measures an absolute position of the bit when the detection signal is received from the detector and an absolute position of the bit when the bit is reliably fitted to the screw; The control unit calculates the difference between the absolute positions of the two bits measured by the bit absolute position measurement unit as the relative position, and the calculated relative position corresponds to the second taught relative position and the second actual measurement. The relative position may be transmitted to the storage unit.

  The screw tightening device according to the present invention can process one step of comparison between the screw lift judgment reference position and the second actual measurement relative position after pass / fail judgment of screw lift performed after tightening to a work, so two conventional steps Can be reduced by one process. Therefore, the screw tightening device of the present invention has an advantage that the time required for the determination of the screw floating immediately after tightening to the work can be shortened as compared with the prior art.

  Further, in the screw tightening device according to the present invention, the thrust to be applied to the bit before measuring each of the first taught relative position, the second taught relative position, the first actually measured relative position, and the second actually measured relative position is The high thrust makes it easy for the bit to be reliably fitted to the actual working screw or teaching screw at these four positions. Moreover, in the screw tightening device according to the present invention, the first taught relative position, the second taught relative position, the first actually measured relative position, and the thrust applied to the bit are switched from the high thrust to the low thrust described above. In order to measure the second measured relative position, the bit is not strongly pressed against the screw support means or the work at the time of measurement of four positions. In other words, the screw tightening device according to the present invention can output a high thrust before measurement of the four positions to reliably obtain a fitting state of the bit and a screw for actual operation or a screw for teaching, and can reduce the thrust. It is possible to measure the four positions while minimizing the deflection of the screw support means or the upper surface of the work. Therefore, the screw fastening device according to the present invention has the advantage that the accuracy of the determination of the thread floating can be improved because the fitting condition and the thrust condition at four positions can be made uniform.

  Furthermore, the screw tightening device according to the present invention reflects the tolerance range defined as the standard dimension of the head height of the screw fitting to the bit and the fitting depth of the head in the first teaching relative position, The reflected range is stored as a screw type discrimination range, and the screw type discrimination range and the first actually measured relative position are compared before tightening to the workpiece. As a result, when the screw is taken out from the screw support means, it is judged whether or not the screw is a genuine part, so that there is also an advantage that it is difficult to occur a situation where a nonstandard screw is tightened to the work.

  Further, in the screw tightening device according to the present invention, the bit relative position measuring unit is configured by a displacement sensor capable of measuring a relative movement distance between the bit and a suction pipe in contact with the upper surface of the workpiece W. As a result, there is no need to calculate the relative movement distance inside the control device to obtain it, so that the configuration of the control device can be simplified and the processing load on the control device can be reduced.

  Furthermore, the screw tightening device according to the present invention may include the bit absolute position measurement unit, and a proximity sensor which is an example of a detector that detects a dog disposed in a suction pipe and emits a signal. The apparatus calculates the difference between the absolute position of the bit at the time of detection of the dog and the absolute position of the bit engaged with the screw in the controller. Thereby, since the relative position of the bit measured by the bit relative position measurement unit can be replaced with the difference of the absolute position, an expensive displacement sensor or the like can be replaced with a relatively inexpensive detector, and a screw There is also an advantage that the cost of the tightening device can be reduced.

It is a schematic explanatory drawing which shows one Embodiment of the screw fastening apparatus which concerns on this invention. It is a block block diagram of a control device concerning the present invention. It is operation | movement explanatory drawing which shows operation | movement of the screw fastening apparatus based on this invention. It is a schematic explanatory drawing which shows another embodiment of the screw-fastening apparatus based on this invention.

  Hereinafter, before describing the embodiment of the screw fastening device 1 of the present invention based on FIG. 1 to FIG. 4, the screw S, the screw St and the work W to be used will be described.

  The screw S (St) is integrally formed with a screw portion formed on the work W and screwed with the screw, and a head set larger in diameter than the screw portion, and the head is A fitting hole is formed to be engaged with the tip of the bit 2 described later. Further, there are two types of the screw S (St), a screw S used at an actual screw tightening operation (hereinafter referred to as an actual operation) and a screw St used at a prior teaching operation. The dimensions of the head of the screw S and the screw St, the fitting hole, the screw portion and the like are all set to the same dimensions.

  The work W is composed of a fastening formed with a female screw and a workpiece formed with a through hole having a diameter larger than the diameter of the female screw, and the workpiece is placed on the fastener and described later. It is held by the clamp unit 60.

  The screw tightening device 1 of the present invention comprises a screw support means 40 for mounting and supporting the head of the screw S or the screw St, a clamp unit 60 for holding the outer periphery of the work W, and the screw S (St). A screw tightening tool 10 having a bit 2 engaged with a fitting hole formed in the head and an adsorption 4 pipe sliding in a direction in which the bit 2 extends, and mounting of the screw tightening tool 10 on a screw supporting means 40 A robot body capable of moving the screw tightening tool 10 above the workpiece W and the screw support means 40 by connecting the lift unit 21 and the lift unit 21 movable in a direction approaching or away from the mounting surface or the upper surface of the workpiece W 26 and a bit relative position measuring unit 8 capable of measuring the height position of the bit 2 moved up and down by driving the elevation unit 21, and instructing the elevation unit 21 etc. Feed composed of controllable controller 30. The each device.

  The screw support means 40 includes a vibrating body 41 capable of vibrating in the front-rear direction, a vibration control device 44 instructing the vibrating body 41 to start or stop vibration, and the screw S or screw St attached to the vibrating body 41. And a receiving block 43 for receiving one screw S or one screw St carried by the carrying rail 42. The receiving block 43 is configured to be able to support by supporting the head of the screw S or the screw St similarly to the transport rail 42, and includes a mounting surface in contact with the head seat surface of the screw S or the screw St. It consists of

  The clamp unit 60 is configured to be capable of holding the work W, and is configured by a so-called receiving jig as shown in FIGS. 1 and 4. In addition, the clamp unit 60 is fixed to the base 100, and can hold the work W so as not to rotate in the screwing direction of the screw S and the screw St.

  The screw tightening tool 10 includes a bit driving motor 3 which is driven to rotate, a bit 2 connected to the bit driving motor 3, and a suction pipe 4 which is inserted through the bit 2 and is slidable along the extending direction of the bit 2 A spring 5 which normally biases the suction pipe 4 toward the tip end of the bit 2, a suction pipe holder 6 which includes the spring 5 and restricts the sliding of the biased suction pipe 4, and the bit drive It comprises a screw tightening tool controller 7 capable of driving and controlling the motor 3 with a predetermined fastening torque and rotational speed.

  The bit drive motor 3 is an AC servomotor provided with an encoder 3a, and a bit 2 is connected to an output shaft (not shown) of the bit drive motor 3. The bit drive motor 3 also outputs to the screw tightening tool controller 7 a rotational pulse signal corresponding to the load current at the time of rotational driving of the bit 2 or the rotational angle of the output shaft output from the encoder 3a.

  The bit 2 is provided at its tip end with a fitting portion 2a engaged with the fitting hole of the screw S and the screw St, and the fitting portion 2a is formed in a convex cross shape. The fitting portion 2a is not limited to a convex cross shape, and may have any shape as long as the fitting holes of the screw S and the screw St are engaged.

  The suction pipe 4 integrally includes a collar portion disposed at one end thereof and a small diameter shaft portion connected to the collar portion, and the bit 2 can be inserted through the entire length of the suction pipe 4 It comprises an insertion hole 4a. The insertion hole 4a is set to a small diameter equivalent to the outer diameter dimension of the bit 2 on the buttock side, and is set to a large diameter capable of containing the head of the screw S on the tip side, and is constituted by multistage holes Ru. Further, on the outer peripheral surface of the suction pipe 4, a suction hole 4b communicating with the insertion hole 4a is disposed, and the suction hole 4b is connected to an air suction means (not shown). Thereby, the screw tightening tool 10 can suction and hold the screw S or the screw St in the suction pipe 4 in response to the operation of the air suction means.

  The spring 5 is a compression coil spring and is disposed such that one end thereof is in contact with the ridge of the suction pipe 4 and is inserted into the bit 2 so that the suction pipe 4 protrudes from one end of the suction pipe holder 6 It is always on. When the end of the suction pipe 4 abuts on the mounting surface of the receiving block 43 or the upper surface of the work W, the spring 5 is pushed by the ridge of the suction pipe 4 and is bent in the compression direction.

  The suction pipe holder 6 includes the spring 5 and the flange portion of the suction pipe 4 and is inserted through the small diameter shaft of the suction pipe 4 to slidably support the suction pipe 4 in the extending direction of the bit 2 ing.

  The screw tightening tool controller 7 is connected to the bit drive motor 3 to rotationally drive and control the bit drive motor 3 based on a preset fastening torque and rotational speed, and to the load current output from the bit drive motor 3 Based on the calculated engagement torque applied by the bit 2. Further, the screw tightening tool controller 7 is configured to output a tightening completion signal to the control device 30 when the predetermined tightening torque is reached.

  The robot body 26 is configured to move the lifting unit 21 supporting the screw tightening tool 10 in the horizontal direction, while the lifting unit 21 is configured to move the screw tightening tool 10 in the lifting direction. .

  The robot main body 26 is connected to an AC servomotor (hereinafter, main body motor 27) which is an example of a drive source which is rotationally driven based on a preset amount of rotation and current, and a lead having a predetermined angle connected to the main body motor 27. It comprises a ball screw shaft 28 provided, and a movable member 29 which can be reciprocated to move over the mounting surface of the receiving block 43 or the work W in response to the rotation of the ball screw shaft 28. The elevating unit 21 is attached to the movable member 29, and the elevating unit 21 reciprocates in the horizontal direction as the movable member 29 moves.

  The main body motor 27 includes an encoder 27 a which outputs a rotation pulse signal corresponding to the rotation of the ball screw shaft 28 to the control device 30. Further, the main body motor 27 is connected to a robot main body drive unit 36 described later, and receives a command from the robot main body drive unit 36 to drive it.

  The elevating unit 21 is connected to the AC servomotor (hereinafter, elevating motor 22), which is an example of a drive source that is driven to rotate based on a preset amount of rotation and current, and a lead having a predetermined angle. A ball screw shaft 23 provided, and a movable member 24 capable of reciprocating in a direction approaching or leaving the mounting surface of the receiving block 43 or the upper surface of the work W in response to the rotation of the ball screw shaft 23 Become. Further, the screw tightening tool 10 is attached to the movable member 24, and along with the movement of the movable member 24, the bit 2 and the suction pipe 4 reciprocate.

  The elevating motor 22 is provided with an encoder 22 a that outputs a rotation pulse signal corresponding to the rotation of the ball screw shaft 23 to the control device 30. The lift motor 22 is supplied with a current necessary for rotational drive from a thrust control unit 31 described later, and is configured to rotate the output shaft according to a preset rotational speed and torque, and is rotating. The load current can be output to the control device 30.

  The bit relative position measuring unit 8 is fixed to the screw tightening tool 10, and is configured to move up and down in a direction approaching or separating from the mounting surface of the receiving block 43 or the upper surface of the work W together with the bit 2 There is. The bit relative position measuring unit 8 is configured as a displacement sensor that measures the elevation distance of the bit 2 with respect to the mounting surface of the receiving block 43 or the upper surface of the workpiece W. This displacement sensor measures the mounting of the measured receiving block 43 The height position of the bit 2 with respect to the surface or the upper surface of the workpiece W is configured to be transmitted to the control device 30.

  The control device 30 calculates and measures the height position of the bit 2 reciprocally moved based on the rotation pulse signal transmitted from the encoder 22a and the angle of the lead of the ball screw shaft 23 stored in advance. A thrust control unit 31 that controls the thrust of a bit 2 that reciprocates by supplying a current set in a measurement unit 35 and a storage unit 33 described later to the elevating motor 22 and a robot main body that controls the position of the robot main body 26 The drive control unit 36, the thrust control unit 31, the screw tightening tool controller 7 and the like are connected to each other, and the control unit 32 that sends operation commands to the connected devices; The input unit 37 to input, the operation parameter input from the input unit 37, the bit relative position measuring unit 8 and the bit A storage unit 33 for storing the measurement result of the absolute position measuring unit 35, comprising a determining unit 34 a threaded lifting screws S with respect to the upper surface of the workpiece W after tightening the screw S into the workpiece W.

  The bit absolute position measurement unit 35 is configured to calculate the position of the movable member 24 that reciprocates based on the rotation pulse signal transmitted from the encoder 22 a and the lead angle of the ball screw shaft 23. Therefore, since the calculated position of the movable member 24 corresponds to the position of the bit 2 which moves together with the movable member 24, the bit absolute position measuring unit 35 measures the position of the bit 2 which reciprocates. Further, the bit absolute position measuring unit 35 stores the position of the bit 2 in a standby state at a predetermined position above the mounting surface of the receiving block 43 or the upper surface of the work W as the origin, and waits for the bit 2 which is the origin. The position of the bit 2 moved from the position SP is calculated as the movement distance from the standby position SP. Therefore, the moving distance of the bit 2 calculated by the bit absolute position measuring unit 35 is the absolute position of the bit 2 with respect to the standby position SP.

  The thrust control unit 31 is configured to be able to control the current supplied to the elevating motor 22, and controls the rotational torque of the ball screw shaft 23 connected to the elevating motor 22. Thereby, the thrust control unit 31 controls the thrust of the bit 2 that is moved up and down with the rotation of the ball screw shaft 23. Further, the thrust control unit 31 compares the absolute position of the bit 2 calculated by the bit absolute position measurement unit 35 with the target position of the bit 2 stored in the storage unit 33, and supplies it to the lift motor 22. It is configured to switch current and configured to be capable of controlling the thrust of bit 2 based on the absolute position of bit 2 moving up and down.

  The robot body drive unit 36 receives information from the body motor 27 of the robot body 26, calculates the position of the screw tightening tool 10 moving in the horizontal direction based on this information, and calculates the calculated position and the storage unit 33. The drive position of the robot main body 26 is controlled in comparison with the set position set in.

  The input unit 37 is configured such that the operation parameters and the like are input using a ten key or the like, and the input contents can be displayed. The operation parameters and the like input from the input unit 37 are written and stored in the storage unit 33 via the control unit 32.

  The storage unit 33 is configured to be able to store various information such as the operation parameter input from the input unit 37 and the set thrust of the bit 2 for a plurality of points. The storage unit 33 is configured to be able to store the relative position of the bit 2 measured by the bit relative position measurement unit 8. Furthermore, the storage unit 33 is configured to be capable of storing a screw type determination range set based on the dimensional tolerance range defined in the JIS standard or the like of the screw S.

  The relative position of the bit 2 stored in the storage unit 33 is the state where the fitting portion 2a of the bit 2 is engaged with the fitting hole of the teaching screw St placed on the mounting surface at the time of teaching operation Measurement in a state where the fitting portion 2a of the bit 2 is engaged with the first teaching relative position FT measured at step S and the fitting hole of the actual work screw S placed on the mounting surface at the time of actual work In the state where the fitting portion 2a of the bit 2 is engaged with the first actually measured relative position FF to be engaged and the fitting hole of the teaching screw St fastened to the work W at the teaching operation and in close contact with the upper surface of the work W The second teaching relative position WT measured and the second measured relative measured in a state where the fitting portion 2a of the bit 2 is engaged with the fitting hole of the screw S fastened to the work W at the time of actual work There are four types with the position WF.

  Further, the screw type determination range stored in the storage unit 33 is a range in which upper and lower limit values related to the height of the head of the screw S and the depth of the fitting hole are taken into consideration. This is a range set in consideration of the first taught relative position FT in a state in which the bit 2 is engaged with the teaching screw St placed and the upper and lower limit values described above.

  The control unit 32 is configured to be able to capture information of each device connected thereto, and is configured to send an operation command to each device based on the operation parameter stored in the storage unit 33. Furthermore, the control unit 32 is configured to be able to perform arithmetic processing using numerical values and the like stored in the storage unit 33, and calculates the difference between the first taught relative position FT and the first actually measured relative position FF and the difference Calculation of the sum with the second taught relative position WT is performed. The difference is referred to as a screw lift determination correction value, and the sum is referred to as a screw lift determination reference position. Further, the control unit 32 is configured to transmit the screw lift determination correction value obtained by calculation and the screw lift determination reference position to the storage unit 33, and the transmitted screw lift determination correction value and the screw lift determination The reference position is stored in the storage unit 33.

  The determination unit 34 determines whether or not the screw S for the actual operation is a screw of a proper size when taking out the screw S for the actual operation from the mounting surface, and after tightening the screw S for the actual operation to the work W It is configured to determine whether or not the screw S is not lifted from the upper surface of the work W. Specifically, the process of determining whether or not the screw is a regular screw is normal if the first actually measured relative position FF is within the screw type discriminating range by comparing the first actually measured relative position FF with the screw type discriminating range. It is determined that the screw is On the other hand, in the thread floating determination process, the thread floating determination reference position is compared with the second actual measurement relative position WF to determine whether the thread floating of the screw S with respect to the upper surface of the workpiece W is successful. The screw lift determination reference position may be a range having a predetermined width. In this case, the range is set in advance in the storage unit 33, and the determination unit 34 determines the third condition. 2. If the measured relative position WF is within the above range, it is determined that the screw is not lifted.

  The operation of the screw fastening device 1 of the present invention will be described based on FIGS. 3 (a) to 3 (d). 3 (a) shows the first taught relative position FT, FIG. 3 (b) shows the second taught relative position WT, FIG. 3 (c) shows the first measured relative position FF, and FIG. 3 (d) shows The state which is each measuring 2nd measurement relative position WF is shown, and the effect | action from teaching operation to real operation is demonstrated in order below.

  First, teaching operation for setting the first taught relative position FT and the second taught relative position WT will be described. As shown in FIG. 3A, the teaching screw St is mounted on the mounting surface of the receiving block 43. At this time, the screw tightening tool 10 stands by at the standby position SP of the bit 2 above the screw support means 40. The controller 30 sends commands to the lift unit 21 and the screw tightening tool controller 7 to operate the lift unit 21 and the screw tightening tool 10. Thereby, the screw tightening tool 10 descends toward the mounting surface and the bit 2 rotates at a predetermined rotation number. With the descent of the screw tightening tool 10, the bit 2 and the suction pipe 4 are integrally lowered without relative movement, and when the tip of the suction pipe 4 abuts on the mounting surface, the bit 2 is thereafter suctioned Move relative to 4 Therefore, the bit 2 engages with the fitting hole of the screw St, and pushes the screw St to bring the head bearing surface into close contact with the mounting surface.

  At this time, the control unit 32 monitors the relative position of the bit 2 measured by the bit relative position measuring unit 8, and if this relative position does not change even after a predetermined time has elapsed, the head bearing surface and mounting surface of the screw St It is determined that the mounting surface is in close contact and the bit 2 and the screw St are engaged, and a stop command is sent to the lifting unit 21 and the screw tightening controller 7. Further, the bit relative position measuring unit 8 sets the height position of the bit 2 relative to the mounting surface in a state in which the lowering and rotation of the bit 2 are stopped and in a state engaged with the screw St mounted on the mounting surface. It sends to the said storage part 33 as a position. The storage unit 33 stores the relative position sent from the bit relative position measurement unit 8 as a first taught relative position FT.

  Next, the screw St is tightened in advance to the work W so that the head bearing surface of the screw St used for measuring the first taught relative position FT is in close contact with the upper surface of the work W. At this time, the screw tightening tool 10 stands by at the standby position SP above the workpiece W. The controller 30 sends commands to the lift unit 21 and the screw tightening tool controller 7 to operate the lift unit 21 and the screw tightening tool 10. Thereby, the screw tightening tool 10 descends toward the upper surface of the workpiece W and the bit 2 is rotated by a predetermined fastening torque. With the descent of the screw tightening tool 10, the bit 2 and the suction pipe 4 are integrally lowered without relative movement, and when the tip of the suction pipe 4 abuts on the upper surface of the work W, the bit 2 is thereafter suctioned It moves relative to the pipe 4. Therefore, the bit 2 is in a state of being engaged with the screw St closely attached to the upper surface of the work W as shown in FIG. 3B in order to keep rotating until the predetermined fastening torque is reached.

  Since the screw tightening tool controller 7 outputs a fastening completion signal to the control unit 32 when the above-mentioned fastening torque is reached, the control unit 32 engages the bit 2 with the screw St and screws the upper surface of the work W It is determined that the head seat of St is in close contact, and a stop command is sent to the lift unit 21. Further, the bit relative position measuring unit 8 sets the height position of the bit 2 relative to the top surface of the work W in a state in which the lowering and rotation of the bit 2 are stopped and in a state engaged with the screw St in close contact with the top surface of the work W The measured relative position is sent to the storage unit 33 as a position. The storage unit 33 stores the relative position measured by the bit relative position measurement unit 8 as a second taught relative position WT.

  In this way, the measurement of the first taught relative position FT and the second taught relative position WT is sequentially performed using the screw St and the bit 2 for the same teaching.

  Next, as shown in FIGS. 3 (c) and 3 (d), the actual operation of taking out the screw S for actual operation from the screw support means 40 and tightening it on the female screw of the work W will be described. The screw support means 40 conveys the screw S tightened to the work W to the receiving block 43 by the conveying rail 42 vibrating. At this time, the screw tightening tool 10 stands by at the standby position SP above the workpiece W. The controller 30 sends commands to the lift unit 21 and the screw tightening tool controller 7 to operate the lift unit 21 and the screw tightening tool 10. As a result, the screw tightening tool 10 descends toward the mounting surface of the receiving block 43, and the bit 2 rotates at a predetermined rotational speed. The bit 2 and the suction pipe 4 are integrally lowered without relative movement, and when the tip of the suction pipe 4 abuts on the mounting surface of the receiving block 43, the bit 2 moves relative to the suction pipe 4 thereafter. . Therefore, the bit 2 is engaged with the fitting hole of the screw S as shown in FIG. 3 (c), and the screw S is pushed to bring the head seat into close contact with the mounting surface.

  At this time, the control unit 32 monitors the relative position of the bit 2 measured by the bit relative position measuring unit 8, and if the relative position does not change even after a predetermined time has elapsed, the head bearing surface and mounting surface of the screw S It is determined that the mounting surface is in close contact and the bit 2 and the screw S are engaged, and a stop command is sent to the lifting unit 21 and the screw tightening controller 7. Further, the bit relative position measuring unit 8 determines the height position of the bit 2 from the upper surface of the work W in a state in which the lowering and rotation of the bit 2 are stopped and in a state engaged with the screw S mounted on the mounting surface. It sends to the storage unit 33 as a relative position. The storage unit 33 stores the relative position sent from the bit relative position measurement unit 8 as a first measured relative position FF.

  After the first actually measured relative position FF is stored, the control unit 32 reads the first actually measured relative position FF and the first taught relative position FT from the storage unit 33, and the first actually measured relative position FF and the first taught Calculate the difference with the relative position FT. Since the calculated difference is the difference between the height position of the bit 2 in a state of being engaged with the screw St and the screw S, the head height and the height of the screw St and the screw S engaged with the bit 2 are obtained. It corresponds to the dimensional difference in the depth of the fitting hole. The control unit 32 sends the difference obtained by this calculation to the storage unit 33, and the storage unit 33 stores this difference as the screw floating determination correction value. Thereafter, the control unit 32 calculates the sum of the screw lift determination correction value and the second taught relative position WT, and sends the sum obtained by the calculation to the storage unit 33. The storage unit 33 stores the sum as a screw lift determination reference position. That is, the screw lift judgment reference position is a value obtained by correcting the second teaching relative position WT by the screw lift judgment correction value, and the dimensional difference of the actual screw S different in the head height and the depth of the fitting hole is taken into consideration. This is a reference value for determining screw lift. The calculation and storage of the screw lift determination correction value and the screw lift determination reference position are always performed before measuring the second actual measurement relative position WF.

  The control device 30 operates the air suction unit and the lifting unit 21 when storing the screw floating determination correction value. As a result, the screw S is sucked into the suction pipe 4 and rises with the screw tightening tool 10 to the standby position SP. Further, the control device 30 operates the robot main body 26 to move the screw tightening tool 10 from the upper surface of the receiving block 43 to the upper surface of the workpiece W.

  Thereafter, the control device 30 sends commands to the lifting and lowering unit 21 and the screw tightening tool 10, lowers the screw tightening tool 10 from the standby position SP toward the female screw of the work W, and the bit 2 has a predetermined fastening torque. Rotate until it reaches. As a result, the bit 2 and the suction pipe 4 are integrally lowered without relative movement, the tip of the suction pipe 4 abuts on the upper surface of the work W, and thereafter the bit 2 moves relative to the suction pipe 4 . Accordingly, as shown in FIG. 3 (d), the bit 2 engages with the fitting hole of the screw S and screws the screw S into the female screw. As a result, the head bearing surface of the screw S comes in close contact with the upper surface of the work W, and the screw S reaches a predetermined fastening torque.

  The screw tightening tool controller 7 outputs a fastening completion signal to the control unit 32, and the control unit 32 having received this sends a stop command to the lifting and lowering unit 21 and the screw tightening tool 10. Further, the bit relative position measuring unit 8 measures the height position of the bit 2 when the control unit 32 receives the fastening completion signal as the relative position from the top surface of the workpiece W, and sends this to the storage unit 33. The storage unit 33 stores the relative position sent from the bit relative position measurement unit 8 as a second measured relative position WF.

  In addition, after the second actual measurement relative position WF is stored in the storage unit 33, the determination unit 34 compares the second actual measurement relative position WF with the thread floating determination reference position, and the second actual measurement relative position WF is determined as thread floating If it does not correspond to the reference position, it is judged that a screw float has occurred, and if it agrees, it is judged that there is no screw float and processing is performed. In addition, when the screw lift determination reference position is set to a range having a predetermined width as described above, the determination unit 34 is configured to release the screw if the second actually measured relative position WF is within the range. It is determined that there is not.

  Thus, the screw tightening device 1 of the present invention calculates the screw floating judgment reference position by comparing the first measured relative position FF with the first teaching relative position FT, the screw floating judgment reference position and the second measured relative position. Comparison with WF is carried out each time the screw S is tightened. Also, the screw tightening device 1 of the present invention measures the first taught relative position FT and the second taught relative position WT using the teaching screw St as described above, and takes out and tightens the actual screw S every time. The first measured relative position FF of the screw S and the second measured relative position WF are measured.

  That is, since the screw fastening device 1 of the present invention determines the difference between the first taught relative position FT measured by the teaching screw St and the first actually measured relative position FF measured by the screw S for actual operation, Not only the dimensional difference between the screws St and S but also the amount of wear of the bit 2 due to the increase in the number of fastenings can be determined. In addition, since the screw tightening device 1 of the present invention processes only the comparison between the second actually measured relative position WF and the screw lift judgment reference position to perform the screw lift judgment, the number of processing steps of the screw lift judgment is It can be reduced from two steps to one step.

  Further, at the time of engagement of the bit 2 with the screw S or the screw St, the thrust control unit 31 controls the lift motor 22 so that the thrust applied to the bit 2 becomes high. Thus, before measuring the first taught relative position FT, the second taught relative position WT, the first actually measured relative position FF, and the second actually measured relative position WF, the bit 2 is a screw St and a screw S, respectively. It is easy to fit in Moreover, since the thrust control unit 31 switches the bit 2 engaged in the high thrust state to a low thrust, the bit relative position measurement unit 8 determines the first taught relative position FT, the second taught relative position WT, Before measuring the first actually measured relative position FF and the second actually measured relative position WF, the bit 2 does not strongly press the mounting surface of the receiving block 43 and the upper surface of the work W via the screw St or the screw S. As a result, since the mounting surface of the receiving block 43 and the upper surface of the workpiece W do not sink deeply, it is possible to perform high-precision screw floating determination and determination as to whether or not the screw is normal.

  The displacement sensor, which is an example of the bit relative position measurement unit 8, includes a contact displacement sensor having a contact that contracts by coming into contact with the mounting surface of the receiving block 43 and the upper surface of the workpiece W, The mounting surface and the non-contact displacement sensor for measuring the distance by irradiating the upper surface of the work W with laser light may be configured, and the relative position of the bit 2 to the mounting surface or the upper surface of the work W is measured It should just be comprised possible.

  Furthermore, as shown in FIG. 4, the bit relative position measuring unit 8 detects a dog 4 c made of metal disposed on the outer periphery of the suction pipe 4 and a dog detected in the control device 30 when detecting the dog 4 c fixed to the suction pipe holder 6. A detector that sends a signal, and a bit absolute position measurement unit 35 that measures the absolute position of bit 2 from the standby position SP of bit 2 from the rotation pulse signal of encoder 22a and the angle of the lead of ball screw shaft 23 It is also good. In this case, the bit relative position measuring unit 8 determines the absolute position of the bit 2 when the dog detection signal is transmitted from the detector and the absolute position of the bit 2 when the screw tightening completion signal is received from the control device 30. It is configured to calculate the difference. Further, since the difference between the calculated absolute positions corresponds to the relative position of the bit 2 with respect to the suction pipe 4, it can be treated as the relative position of the bit 2 with respect to the mounting surface of the receiving block 43 or the upper surface of the work W. Therefore, the bit relative position measuring unit 8 provided with the detector is the mounting surface of the receiving block 43 or the work W in the same manner as the bit relative position measuring unit 8 provided with the non-contact type displacement sensor or the contact type displacement sensor described above. It is configured to be able to measure the relative position of bit 2 with respect to the top surface of. Further, the difference between the absolute positions calculated by the bit relative position measuring unit 8 is stored as the first taught relative position FT, the second taught relative position WT, the first actually measured relative position FF, and the second actually measured relative position WF. Sent to The detector can be configured by a proximity sensor capable of detecting a metal as shown in FIG. 4 or a photoelectric sensor that detects and transmits a dog when the optical axis is interrupted by the dog 4c.

  Further, the robot main body 26 is not limited to the above-described configuration, and may be configured to be movable to the upper surface of the receiving block 43 or the upper surface of the workpiece W, respectively. For example, the robot body 26 may be configured as a so-called articulated robot.

Reference Signs List 1 screw tightening device 2 bit 4 suction pipe 8 bit relative position measurement unit 10 screw tightening tool 21 lifting unit 30 control device 31 thrust control unit 33 storage unit 34 determination unit 35 bit absolute position measurement unit 40 screw support means W work S screw Used during actual work)
St screw (used for teaching work)
SP standby position

Claims (5)

A screw tightening tool rotatably provided with a bit engaged with a screw, an elevation unit connected with the screw tightening tool and capable of moving up and down in a direction in which the bit extends, an elevator unit connected with the screw tightening tool Alternatively, the screw tightening device includes a robot body movable above the workpiece, and a control device for driving and controlling the robot body, a screw tightening tool, and a lifting unit, and taking out the screw from the screw support means and tightening the workpiece.
It comprises a bit relative position measurement unit which measures the elevation position of the bit as a relative position to the mounting surface of the screw support means or the upper surface of the work,
The bit relative position measurement unit measures the relative position with respect to the mounting surface as a first taught relative position at the time of teaching work, and measures it as a first actually measured relative position at the time of actual work, while the relative to the upper surface of the work The position is measured as a second teaching relative position at the time of teaching work, while it is measured at the time of the actual work as a second actual measurement relative position,
The control unit calculates a difference between the first taught relative position and the first measured relative position, and calculates a sum of the difference and the second taught relative position, and a screw calculating the calculated sum A storage unit that stores the float determination reference position and a determination unit that determines whether or not there is thread floating on the upper surface of the workpiece by comparing the screw float determination reference position with the second actual measurement relative position. Screw tightening device. The elevating unit comprises an elevating motor for pulsating the amount of rotationally driven rotation to the outside, a ball screw shaft connected to the elevating motor and having a predetermined lead, and a ball screw shaft engaged with the ball screw shaft. And a movable member movable along a direction in which the
The control device changes a current supplied to the elevating motor and switches a thrust control unit that switches and controls a thrust of the elevating bit, a pulse output of the elevating motor, and a lead position of the bit based on a lead of the ball screw shaft. And a bit absolute position measurement unit that measures as the absolute position of the bit,
The thrust control unit switches the thrust of the bit from high thrust to low thrust before measuring the first taught relative position, the first measured relative position, the second taught relative position, and the second measured relative position. The screw tightening device according to claim 1, which is controlled. The storage unit is configured to store a screw type determination range set in advance based on a standard dimension that defines a head height of a screw and a depth of a fitting hole of a screw to be engaged with the bit;
The screw according to claim 1 or 2, wherein the judgment unit judges the dimension of the screw taken out from the screw support means by comparing the screw type discrimination range with the first measured relative position. Tightening device. The screw tightening tool is provided with a suction pipe which slides in a direction in which the bit extends and moves relative to the bit and can suction the screw .
The screw fastening device according to any one of claims 1 to 3, wherein the bit relative position measuring unit is configured by a displacement sensor that measures the moving distance of the suction pipe moved relative to the bit. . The elevating unit comprises an elevating motor for pulsating the amount of rotationally driven rotation to the outside, a ball screw shaft connected to the elevating motor and having a predetermined lead, and a ball screw shaft engaged with the ball screw shaft. And a movable member movable along a direction in which the
The control device includes: a bit absolute position measurement unit configured to measure an absolute position of the bit relative to a standby position of the bit based on a pulse output of the lift motor and a lead of the ball screw shaft;
The screw tightening tool slides in a direction in which the bit extends and moves relative to the bit , and detects a suction pipe capable of sucking the screw and the suction pipe which has started to move relative to the bit. And a detector for emitting a detection signal to the controller.
The bit absolute position measuring unit is configured by measuring an absolute position of the bit when the detection signal is received from the detector and an absolute position of the bit when the bit is reliably fitted to the screw.
The control unit calculates the difference between the absolute positions of the two bits measured by the bit absolute position measurement unit as the relative position, and the calculated relative position corresponds to the second taught relative position and the second measured relative position. The screwing device according to any one of claims 1 to 3, wherein the screwing device is transmitted to the storage unit as

Images